Top Quark Mass Calibration for Monte Carlo Event Generators

TL;DR

This paper introduces a calibration method to relate the Monte Carlo top quark mass parameter to a field theory mass, using QCD predictions and event generator data, to improve the accuracy of top mass measurements.

Contribution

A new calibration procedure that connects the Monte Carlo top mass parameter to a well-defined field theory mass using hadron level QCD predictions and event generator fits.

Findings

$m_t^{ m MC}$ differs from the pole mass by 900/600 MeV.

$m_t^{ m MC}$ agrees with the MSR mass within uncertainties.

Calibration reduces ambiguity in top mass measurements.

Abstract

The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator, $m_t^{\rm MC}$. Due to hadronization and parton shower dynamics, relating $m_t^{\rm MC}$ to a field theory mass is difficult. We present a calibration procedure to determine this relation using hadron level QCD predictions for observables with kinematic mass sensitivity. Fitting $e^+e^-$ 2-Jettiness calculations at NLL/NNLL order to Pythia 8.205, $m_t^{\rm MC}$ differs from the pole mass by $900$/$600$ MeV, and agrees with the MSR mass within uncertainties, $m_t^{\rm MC}\simeq m_{t,1\,{\rm GeV}}^{\rm MSR}$.